The oldest civil war in the world is being fought, on one side, by men who wander like demented hospital orderlies across the primordial wastes of Africa.

I follow them one hot morning as they flee a government ambush in the oil fields of southern Sudan. One of their comrades has just been shot dead, his body abandoned on a parched savanna that hides nearly 20 billion dollars' worth of low-sulfur crude. We retreat for hours under a scalding sun, crossing in the process a vast, cauterized plain of cracked mud. I pause a moment to watch them: an ant-like column of rebels dressed in bizarre homemade uniforms of green cotton smocks and white plastic slippers, limping into the heat waves of distance. Five casualties bounce in stretchers. They suffer their bullet wounds in silence. A boy marching in front balances a car battery on his head. He is the radio operator's assistant. Every few hundred yards he puts the battery down and empties blood out of a shoe.

When we finally reach a tree line, the fighters strip off their clothes and jump into a bog. The water stinks. It is infested with larvae of guinea worms, which, once ingested, burrow painfully through the body to the legs, and are extracted by making a small incision; you reel the worm out slowly, day after day, by winding it on a small stick. All around us, half-naked people move feebly through the thorn forest: ethnic Dinka herders displaced from the contested oil fields by fighting between rebels and the central government based in the faraway capital, Khartoum. Their children, stunted and ginger-haired from malnutrition, clamber in the trees. They are collecting leaves to eat. This awful place, I learn, is called Biem—a safe haven, such as it is, of the 40,000-strong Sudan People's Liberation Army.

"You cannot reclaim what is lost," the sweating rebel commander says, squatting in the shade of an acacia, "so you just keep fighting for what little you have left."

He is trying to console himself. But I see little solace for the epic tragedy of Sudan. It is April 2002, and Africa's largest country is lurching into its 19th uninterrupted year of warfare—the latest round of strife that has brutalized Sudan, off and on, for most of the past half century. More than two million Sudanese are dead. We just left the latest fatality sprawling back in the yellow grasses, a bullet through his brain. And thousands of scarecrow civilians stagger through the scrub, starving atop a lucrative sea of petroleum.

Go to the heart of Sudan's bloody civil war and experience the human tragedy and indomitable spirit of the Nuba people.

Photographer Randy Olson reads from his journal and reveals the challenges of working in the midst of danger and chaos.

For 37 years the people of Sudan have been engaged in a civil war over ethnic and religious differences, power, and control of oil. How can a nation so embroiled find its way to peace?

In More to Explore the National Geographic magazine team shares some of its best sources and other information. Special thanks to the Research Division.

Its once-beautiful coral buildings are now crumbling ruins, but the ancient port of Suakin Island remains a symbol of the ebb and flow of Sudanese culture.

The island sits just 36 miles (58 kilometers) south of Port Sudan on the country's eastern Red Sea coast. For nearly 600 years—off and on—it was the center of a trading network that stretched from eastern Sudan to India and China, Egypt and Iraq in the north, and Ethiopia and Kenya to the south. As the eastern outlet for the Nile Valley, Suakin's strategic location helped to bridge Asia, Africa, and several Middle Eastern countries. It became a gateway for Islam to reach traditional African religions. When the Ottoman Turks rose to power in the 16th century, Suakin provided African pilgrims on their way to Mecca a safer alternative than the traditional route through occupied Egypt. Archaeologists believe that Ramses III used the island as a trading port as far back as the 10th century B.C.

Suakin peaked in prosperity during the boom years of the slave trade in the 19th century. But the development of steamer ships, the opening of the Suez Canal in 1869, the creation of Port Sudan in the early 1900s, and encroaching coral reefs that made the shallow, narrow harbor entry difficult to navigate diminished Suakin's main livelihood. Finally, after years of toil and triumph and a brief resurgence in the 1920s, the island town declined and descended into decay. All that remains of Suakin are piles of rubble and the silent, shadowed remnants of a historic city.

—Meaghan Mulholland

Oil and Human Rights Maps in Central and Southern Sudan.www.rightsmaps.com/html/sudmap1.htmlAccess maps and satellite views of oil concessions, ethnic geography, and areas controlled by the government and rebel forces.

Sudan Netwww.sudan.netGet the latest news on Sudan compiled from newspapers around the world and press releases from the government and rebel groups.

Keith-Roach, Edward. "Adventures Among the 'Lost Tribes of Islam' in Eastern Darfur: A Personal Narrative of Exploring, Mapping, and Setting Up a Government in the Anglo-Egyptian Sudan Borderland," National Geographic (January 1924), 41-73.